Malacia, 27, has signed a one-year contract with the Ohio club.
“We are excited to add a player of Tyrell's experience,” FC Cincinnati General Manager Chris Albright said on the club website.
“He's played at the highest levels of the game and understands the demands of competing in those environments. His quality on the ball, defensive instincts, and team-first mentality are a welcome addition to the group, and we’re happy to have him in Cincinnati.”
Malacia left Manchester United upon the expiry of his contract last summer. The former Netherlands international joined the Red Devils from Feyenoord for €15 million in 2022 and played 39 games in his first season in Manchester, but suffered a severe knee injury in the summer of 2023.
After several setbacks, Malacia made his return to the pitch after a 500-day absence, but never broke through in the first team again, playing a total of 12 games for Manchester United after his injury.
FC Cincinnati are currently ninth in the Eastern Conference with 32 points after 24 games.